Solid ink jet printing machines include printheads that include one or more ink-filled channels communicating at one end with an ink supply chamber or reservoir and having an orifice at the opposite end, commonly referred to as the nozzle. An energy generator, such as a piezo-electric transducer, is located within the channels near the nozzle to produce pressure pulses. Another type system, known as thermal ink jet or bubble jet, produces high velocity droplets by way of a heat generating resistor near the nozzle. Printing signals representing digital information originate an electric current pulse in a resistive layer within each ink passageway near the orifice or nozzle, causing the ink in the immediate vicinity to evaporate almost instantaneously and create a bubble.
One example of a printhead assembly for solid ink printing machines is shown in FIG. 1. The assembly 10 comprises a series of functional plates, each performing an ascribed function for controlled dispensing of the molten ink onto a substrate passing by the assembly. In a particular embodiment, the printhead assembly 10 includes a jetstack plate assembly 11, a piezo-electric transducer plate 13 carrying PZT slabs 12, a stand-off plate 14, a circuit board 15, a diverter plate 17, a manifold plate 19 and a compliant outer wall 20. The stack for the printhead assembly 10 may also include a discrete adhesive layer 16 that adheres the diverter plate 17 to the circuit board 15, and an adhesive layer 18 that adheres the diverter plate 17 to the manifold 19.
The plates a typically formed of aluminum and/or stainless steel. In some printhead assemblies, the metallic plates are brazed together. However, improved printheads have utilized polymer adhesive films to join the metal components of the stack. In particularly, an adhesive film is applied between adjacent printhead components and the stack is heated and compressed until the adhesive cures. One adhesive commonly used adhesive is a thermoset acrylic polymer known as R1500. It has been found that polymer films, such as the R1500 film, may have a less than optimal interface between the polymer and the metal itself so that the adhesive interface may shear under higher loads.
Consequently there is a need for an improved interface between the adhesives used to fix a printhead stack together and the metal plates in the stack.